1. Field of the Invention
The present invention relates to an independent spring-loaded tube assembly that can be inserted into any commercially or custom-designed container or rack.
2. Description of the Related Art
In many manufacturing plants, work-in-process, also known as work pieces, are placed into or removed from a lowest part of a container or holding apparatus when an employee xe2x80x9cpearl divesxe2x80x9d, i.e. leans forward and bends down into the container to place or remove a work piece from the bottom.
Depending upon the number of times that an employee repeats this motion by so-called xe2x80x9cpearl divingxe2x80x9d, strain in the back, legs, and arms often results from the amount of leaning and bending. Also, the size of each work-in-process determines the rapidity with which strain will develop. Thus, pearl diving will cause physical trauma and other injuries that frequently lead to lost production time, workman""s compensation claims, and occasional litigation.
This problem has been tackled previously. Although various attempts have been made to come up with a viable solution, none of them are known to have met with much success because of their limited applications.
In U.S. Pat. No. 608,701 issued on Aug. 9, 1898, Morse discloses a refrigerator case for shipping perishable articles that are packed onto a false bottom that is raised and lowered in-response to the weight thereon. Dual-acting springs move the bottom up and down.
In U.S. Pat. No. 811,651 issued on Feb. 6, 1906, Miller discloses a box having a spring-loaded bottom which raises and lowers fruit for display. A single spring is coiled around a central tube to move the bottom.
In U.S. Pat. No. 1,623,270 issued on Jun. 14, 1927, Bradley et al. disclose a hamper for holding miscellaneous articles. The hamper has a spring-loaded bottom that is movable to such a height so as to make the articles readily accessible to an operator. The bottom may be elevated or depressed at the will of the operator without much physical effort.
In U.S. Pat. No. 2,319,872 issued on May 25, 1943, Leonard discloses a box having a spring-loaded tray which raises and lowers empty bottles. The spring is hooked for attachment over the top edge of the bin. The opposite end of the spring is riveted. However, no explanation is given as to how the bottom of the angle brace is attached to the container.
In U.S. Pat. No. 2,468,115 issued on Apr. 26, 1949, Saul, Jr., discloses a bin with a movable bottom. The bin was designed with a set of tubes as an integral part of the bin. The springs are also compression-type springs and they are kept at the bottom with a bolt. The slots are only extended part way down the tube, thus causing a portion of the bin to be unusable.
In U.S. Pat. No. 2,662,802 issued on Dec. 15, 1953, Gibbs discloses a self-leveling dispenser for bottles. This dispenser is also a specific container built to have a tray that raises or lowers. The spring is enclosed in a containment device separate from the tray. Gibbs also shows a specific leveler that rides on a plate which keeps the unit from binding.
In U.S. Pat. No. 2,692,177 issued on Oct. 19, 1954, Larsen discloses a design similar to Gibbs but changed in a way so that a leveler rides a bracket. However, Larsen still uses the specific design of Gibbs for the spring mechanism.
In U.S. Pat. No. 2,717,085, issued on Sep. 6, 1955, Waddington discloses a self-leveling dispensing apparatus. This apparatus employs a spring-loaded shelf which uses a leveler to keep the shelf steady. Waddington makes a specific point that his device keeps the shelf from binding.
In U.S. Pat. No. 2,802,575 issued on Aug. 13, 1957, Harrison discloses an elevation adjuster stand. This stand shows one tube inside another tube with springs inside. This arrangement allows the shelf to travel the full length of the tubes. It is assumed that this stand is intended for magazines and newspapers. If it was designed for a specific application, a size change could affect the mechanics.
In U.S. Pat. No. 3,666,114 issued on May 30, 1972, Davis discloses a display rack with a spring-assisted shelf. This self-contained unit was designed for use as a self-leveling device utilizing a support frame to house the springs. The tubes housing the spring incorporate a pulley at the top. A portion of the tray extends into the tube as well.
Although the broad concept of providing a container with a spring-loaded, weight-responsive bottom is disclosed in each of the older U.S. Patents discussed above, unfortunately, none of these early prior art devices are considered satisfactory for a fast-paced assembly line in a modern production plant. Moreover, none of them either disclose or suggest the particular details of the present invention which is a tube assembly attached to a shelf for solving the problem of pearl diving mentioned initially.
Thus, it remains a problem in the prior art to stop the practice of pearl diving in all types of containers or racks so that lost time and compensation claims therefor are eliminated or at least reduced.
A primary object of the present invention is to provide a spring-loaded tube assembly which makes the practice of pearl diving unnecessary so that lost production time and workman""s compensation claims for back and related leg muscle strain are eliminated. It is also an object to use the tube assembly in any container or rack without the loss of flexibility or space in the container or rack.
This object is accomplished by providing an assembly with a combination of two or more extruded plastic tubes. A spring is housed in an inner chamber and is attached at a bottom of the chamber by a Mechanical fastener. A cable is attached to a top of the spring by a swaged fastener and extends upwardly over a pulley. The cable is then inserted into an outer chamber. One end of this cable has a swaged fastener and ring attached thereto. A quick-link is attached to the ring and extends out through a slot formed in one of the extruded tubes for attachment to a shelf inside a container. Each corner of this shelf has a slide ring assembly which enables the shelf to float independently as weight is applied. This action reduces any distortion that can occur in the shelf when the shelf is not loaded in a uniform manner. Also, the ability of the shelf to tilt at any or all corners prevents it from binding to the sides of the container as work-in-progress is loaded or unloaded. The outer chamber of each tube is adjacent to the shelf while the inner chamber of each tube is spaced farther from the shelf.
A key advantage of this invention is that this unit having four corner spring posts and the shelf can be inserted into any existing commercial or custom-designed container without the need for making additional modifications. The addition of this unit will help prevent back strain and similar muscular injuries to workers who are constantly bending over to retrieve or store articles in the container by placing either the empty shelf or a top of the load on the shelf at a comfortable waist level.
It is another object of the invention to provide an apparatus which is simplistic in its operation. The weight of the work pieces being placed onto or taken from the shelf makes it go down or up, respectively. In other words, the continual addition of items makes the shelf drop and the continual removal of items therefrom makes the shelf rise. The springs maintain the level of work-in-process at an ergonomically acceptable height that is typically set at 30 to 36 inches from the floor.
It is a further object of the invention to ensure that all work-in-progress will be located at or near the acceptable height recommended by optimal ergonomic guidelines either by attaching the shelf to a set of two or more spring-loaded tubes attached to the shelf or by placing them into a container or rack, thus making it a self-contained independent unit which may be portable.
These two embodiments are examples that could be used to accomplish similar results. Instead of only two tubes, three or preferably four or even five tubes may be used. The way that the springs inside the tubes control shelf action, and the possibility that the weight of the product may very greatly, make this invention unique. For example, the springs compensate for different container weights and contents from light, i.e., about 25 pounds, to heavy, i.e., about 1,250 pounds. Furthermore, the rate of speed for raising and lowering the shelf is controlled by spring length and gauge that determine capacity and elongation.
Thus, the ability to work with loads of varying weights, the enclosure of the springs in protective aligning tubes, the simple way of attaching the shelf inside the container, and the ease of changing the springs to accommodate different work needs are primary features of the invention.
These features and other advantages of the invention will become apparent from a review of the attached drawings in conjunction with a careful study of the following detailed description of the preferred embodiments.